Tankless water heater hot water return system

ABSTRACT

A tankless return hot water return system to facilitate whole-house or whole-building hot water return recirculation used in conjunction with tankless water heaters. The system is designed to compensate for tankless head losses and to protect the tankless heat exchanger. The system has a hot water return by-pass for heat exchanger protection. The invention utilizes the tankless water heater as the heating source for the hot water return and eliminates the need and use of tank-type water heaters for tankless hot water return recirculation. The system is self-contained with built-in temperature sensing and does not require any auxiliary controls, sensors, switches, timing mechanisms or remote activation. The system is energy efficient and water conservative.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present utility patent application claims the advantage ofprovisional applications #60/914001 and #60/913998 both filed Apr. 25,2007.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to plumbing systems and particularly to atankless water heating hot water return system which comprises aplumbing system having a hot water recirculating line which bringsunused cooled “hot” water from the hot water supply lines back to thehot water heater so that it may be reheated and redirected to the hotwater outlet, thereby conserving water.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 1.98

Various hot water recirculating systems have been previously designed,some for boiler-tank systems as documented in U.S. Pat. No. 1,780,379 byDurdin, Jr. and also for use with tank-type water heaters such asdocumented in U.S. Pat. No. 4,201,518 by Stevenson.

Two of the biggest concerns we face today are escalating energy costsand water conservation. Domestic hot water systems for both commercialand residential applications consume energy for heating and cancontribute to waste of fresh water. Hot water systems experience heatlosses, increasing energy usage. Systems that are not recirculatedrequire running water down the drain until hot water arrives.

Tankless water heaters are becoming a trend in domestic water heating.They are displacing tank-type water heaters due to their size,efficiency and due to the fact that they do not experience the stand-bylosses of tank-type water heater technology. However, tankless waterheaters do not accommodate simple, whole-house hot water return like atank-type heater does. There are several methods for hot water returnthat are commonly used with tankless water heaters. These methods wereoriginally designed for tank-type technology and have many drawbackswhen applied to tankless systems.

The design of a tankless water heater uses a copper heat exchanger totransfer heat into the flowing water. The burner transfers heat into theflowing water through the copper heat exchanger. The heat exchanger hasa very high head loss and this complicates simple hot waterrecirculation. Attempts have been made to come up with a method toresolve these drawbacks. These methods either use enormous amounts ofenergy, flow directly into the tankless heater and reduce or void itswarranty, or service a single fixture group.

The first method has been to directly recirculate back into the waterheater. This method, originally designed for a tank-type water heater,is documented in U.S. Pat. No. 5,735,291 by Kaonohi. This method isextremely stressful to the copper heat exchanger of the tankless heater.It is not designed to withstand direct circulation. This method ofrecirculation has been deemed by tankless manufacturers as detrimentalto their heat exchangers. As a result, tankless manufacturers eithergreatly reduce or void their heat exchanger warranties if they areinstalled with Direct Recirculation.

The next method commonly used is to employ a tank-type water heater tofacilitate hot water return. The tank-type water heater allows hot waterto recirculate and functions as a buffer. The tank-type heater does nothave the head losses associated with tankless heaters, so it can acceptcirculation. This method does protect the tankless heater's heatexchanger, but it has astronomical energy consumption. The tank-typewater heater method totally defeats the purpose of “Tankless” waterheating and will add back stand-by losses to the system. The KW input ofan electric tank-type water heater is not enough to efficiently heat thereturn line. The electric element remains on any time the return pump isactive. This method actually uses more energy than a standard tank-typewater heater being used as the only water heating source. This methodalso does not maintain system temperatures due to the fact that thelow-input tank-type water heater is trying to heat the return line, notthe Tankless heater.

The last method that is commonly used is to employ a under-sinkrecirculation system. These systems draw hot water from the hot waterpipe and circulate the flowing water into the cold water supply. Thesesystems were originally designed for use with tank-type water heatersbut can be applied to tankless heaters.

Several of these prior art systems are documented, such as U.S. Pat. No.5,323,803 by Blumenauer, U.S. Pat. No. 5,277,219 by Lund, U.S. Pat. No.5,941,275 by Laing and U.S. Pat. No. 5,829,475 by Acker. These systemscan deliver hot water, but only to a specific fixture group. They do notaddress whole-house recirculation and require activation. The systemsare either activated by flow, temperature, manual push button or motionsensors. These systems can over-heat the cold water supply resulting inincreased energy costs. They can be useful in systems that cannotaccommodate a dedicated hot water return line.

Many gallons of water are wasted by turning on hot water taps andshowers and waiting until the cold water standing in the hot water pipespasses through the tap. Without a recovery system the water has simplybeen allowed to run down the drain thus not only wasting good water butoverburdening waste water treatment plant with additional volumes ofwater.

Currently the prior art systems must have a storage tank or electricstorage heater to properly operate a recirculation system with tanklesswater heaters.

U.S. Patent Application #20060022062, published Feb. 2, 2006 by Morris,is for an on-cue hot-water circulator consisting of an electroniccontrol module, a manifold containing a check valve and/or a normallyclosed solenoid valve, a flow switch, and a high-performance pump (not atypical circulation pump), that is also designed or selected for itsability to allow water to pass through it with little or no restriction,when not operating. In a retrofit installation, the cold-water supplyline is used for returning purged water to the water heater.

Prior Art System with Basic HWR with Timer, Flow Switch—use of ColdWater Line

U.S. Patent Application #20030089399, published May 15, 2003 by Acker,provides a smart demand hot water recirculation system includes a hotwater source and at least one plumbing fixture having a hot water inlet.A pump is provided to circulate water to and from the fixture and acontroller, responsive to a plurality of a generated control signals,based on fixture use, activates the pump based on a statistical analysisof control signal timing.

Demand Type System Requiring External Controls/Basic HWR System

U.S. Patent Application #20050006402, published Jan. 13, 2005 by Acker,shows a method of operating a plumbing system and a hot waterrecirculation system. The system generally comprises a hot water source,for example a water heater, such as for example, a gas, oil, solar orelectric tanks or tankless heater, interconnected by means of pipes withplumbing fixtures, said pipes providing conduit means for enablingcirculation of hot water from said hot water source to each plumbingfixture and return to the hot water source. The pipes are thus in fluidcommunication with the hot water source and the plumbing fixtures insuch a way as to establish a hot water loop. This is mainly for a PumpController that creates its own operating pattern

U.S. Patent Application #20060230772, published Oct. 19, 2006 byWacknov, claims a system and method for efficient and expedient deliveryof hot water which detects and anticipates fluid flow in a pipeutilizing a sensor, a processor, and a time base. In an alternatesystem, a recirculation extension is included in system, wherein anadditional plumbing line attaches at a point of the hot water plumbingsystem. The point of attachment is selected to include as much of thehot water distribution system as possible between hot water heater andthe point of attachment. The recirculation plumbing extends from thepoint of attachment and returns to hot water heater at a second point.The hot water return is shown as a separate conduit into the hot waterheater. A pump is often included to move water. The pump may runcontinuously or be regulated by a number of control schemes.

Another Processor Pump Controller/Timing Sensitive

U.S. Pat. No. 5,277,219, issued Jan. 11, 1994 to Lund, is for a hotwater demand system suitable for retrofit. A control system causes thepump to circulate water from the hot water line into the cold water lineand back to the hot water source when a hot water valve on said plumbingfixture is turned on. A temperature sensor stops the pump, via thecontrol system, to prevent heated water from being circulated throughthe cold water delivery lines.

Basic Demand System for Single Fixture Requiring Activation, RemoteSensors and Utilizing the Cold Water Piping.

U.S. Pat. No. 4,201,518, issued May 6, 1980 to Stevenson, shows arecirculating hot water system which includes a hot water supply pipeand a hot water return pipe connected in a loop between a hot wateroutlet of a hot water tank and a return inlet to that tank. Anelectrically controlled recirculating pump is placed in the return pipebetween the inlet to the hot water tank and the supply pipe, which hashot water taps located at various points along it.

Basic HWR for Tank-Type Heaters Requiring Manual Activation

U.S. Patent No. 5,572,985, issued Nov. 12, 1996 to Benham, claims arecirculating system with a by-pass valve. The recirculating hot watersystem comprises a boiler for heating a continuous supply of hot water,a recirculating water line comprising a supply line connected to anoutlet of the boiler for conveying water from the boiler to at least oneuse station and a return line for returning water not consumed at thestation to the boiler, a circulating pump in the return line forcontinuously circulating water in the water line, a by-pass circuit forby-passing the recirculating line connected at an outlet of the pump andan inlet to the pump, and a by-pass valve in the recirculating line atthe by-pass line for directing water at a predetermined temperaturethrough the by-pass line. For continuous circulation only/Special Valvethat regulates a variable flow rate/By-Pass is for regulation oftemperature

U.S. Pat. No. 4,606,325, issued Aug. 19, 1986 to Lujan, Jr., describes awater conservation system for use in residential dwellings or otherbuildings having a hot water distribution system. The system conserveswater which is typically wasted by users while waiting for warm water toflow from a hot water faucet. The system provides a recirculating cooledhot water supply line from the cooled-off end of a hot water line backto the hot water heater of the hot water distribution system. The systemis provided with a plurality of control means to electrically energizethe system's recirculating pump so long as a pressure switch detectsthat the main water supply is providing sufficient water pressure to thesystem. In operation the recirculating pump opens a check valve in therecirculating line and closes the check valve in the main water supplyline and recirculates the cooled hot water back to the hot water heaterfor ultimate use. If the main water supply has insufficient pressure,the recirculating cooled hot water system is non-functional.

Basic HWR with a Pressure Switch Required to Activate, Based on IncomingWater Pressure.

U.S. Pat. No. 5,829,475, issued Nov. 3, 1998 to Acker, discloses anon-demand zone valve recirculation system. The zone valve hot waterrecirculation system generally includes a hot water source, such as anelectric or gas water heater, a conduit for enabling circulation of hotwater from hot water source to one or more plumbing fixtures andrecovery of water to the hot water source, a pump for acceleratingdelivery of hot water to the fixtures and, importantly, a zone valve forpreventing flow of water into the hot water source during standbyperiods of the hot water source. A controller, which may include anelectronic timer, is provided for causing the zone valve to open andclose and the pump to start and stop.

Demand Type System that Functions as an Inlet Booster Pushing WaterTowards the Fixture. It also Closes and Controls the HWR Line.

U.S. Pat. No. 4,750,472, issued Jun. 14, 1988 to Fazekas, indicates acontrol means and process for domestic hot water re-circulating systemhaving a hot water supply pipe and a hot water return pipe connected ina loop between a hot water outlet of a hot water tank and a return inletto that tank, and having an electrically controlled recirculating pumpin the loop, for keeping sufficient circulation in the loop as to assuresubstantially instant dispensing of water of a desirably hightemperature. The control governs the operability of the recirculatingpump, causing it to operate for a pre-established time period asdetermined by the amount of time required to bring the supply pipeportion of the recirculation loop up to desired maximum operatingtemperature. After the supply pipe portion of the recirculation loop isbrought up to the desired maximum operating temperature, the controlswitches off the recirculating pump for a pre-established time perioddetermined by the heat-holding capability of the supply side of therecirculating loop, and the minimum desired operating temperature of thesupply portion of the recirculating loop.

Tank-Type HWR Based on Timing, NOT Temperature.

U.S. Pat. No. 1,780,379, issued Nov. 4, 1930 to Durdin, Jr., puts forthan automatically controlled hot water circulating system. The hot wateris supplied from the hot water tank or reservoir through a supply pipeto the hot water faucets and then is returned by way of a return pipethrough a pump back to the hot water reservoir. The pump is operated tocirculate water from the top or hot water side of the storage reservoirback to the bottom, so that hot water is continuously availablethroughout the length of the supply pipe.

Basic HWR with Boiler and Storage Tank. Does not Apply to Tankless HWR.

U.S. Pat. No. 7,036,520, issued May 2, 2006 to Pearson, Jr., concerns ahot water heater recirculation system and method. The hot waterrecirculation system includes a source of hot water, a fixture, a fluidcircuit, a fluid pump, and an electrical circuit sensor. The fixture isremote from the source of hot water and is configured to dispense hotwater. The fluid circuit extends from the source to the fixture fordelivering hot water to the fixture. The fluid circuit returns to thesource for recirculating hot water in the fluid circuit back to thesource for reheating. The fluid pump is configured for recirculating hotwater through the fluid circuit. The electrical circuit sensor isconfigured to detect operation of an electrical circuit proximate thefixture and associated with a user operating the fixture. The electricalcircuit sensor is further configured to initiate operation of the fluidpump responsive to detected operation of the electrical circuit toinitiate hot water recirculation.

Tank Type HWR with Remote Activation Required (Motion Sensing)

U.S. Pat. No. 4,945,942, issued Aug. 7, 1990 to Lund, illustrates anaccelerated hot water delivery system for providing hot water to aplurality of plumbing fixtures from a hot water source. Flow switchmeans are provided to enable a pump to circulate hot water to theplumbing fixtures in response to water being withdrawn from a plumbingfixture. In addition, the hot water source may include a hot waterrecovery apparatus for withdrawing hot water from circulation pipessubsequent to cessation of water flow from a plumbing fixture.

Flow Activated—Booster Type System

U.S. Pat. No. 4,936,289, issued Jun. 26, 1990 to Peterson, is for ausage responsive hot water recirculation system. The energy conservationapparatus controls the operation of a recirculating hot waterdistribution system which comprises of a hot water heater having anoutlet and an inlet; a return pipe interconnecting the end of the supplypipe back to a tee on the makeup water inlet to form a loop; and anelectrically operated recirculating pump in the loop, usually on thereturn pipe, that circulates the hot water around the loop. Thus hotwater is available anywhere in the system without having to firstdischarge any cooled hot water that has been standing in the piping. Theinvention consists of a sensitive flow sensor or usage detection devicelocated on the unheated makeup water supply and connected to acontroller. The controller turns on the recirculating pump only when hotwater is draw from any of the usage points. The invention saves energyby reducing the heat loss from the hot water distribution system.Options are available to prevent false activation due to system leakage,to prevent activation on very short usages, to turn off or prevent theactivation of the system if the distribution system is already hot, torun the pump for a preset minimum time and/or to monitor leakage orsensor problems in the system.

Not Basic HWR—Activated by Flow and Turns Off when CW Stops.Demand/Booster Type

U.S. Pat. No. 4,628,902, issued Dec. 16, 1986 to Comber, provides a hotwater distribution system for providing almost instantaneous supply ofhot water at a hot water usage outlet. The system of the inventioncomprises a closed loop and a pump circulating hot water in the closedloop from a supply of hot water and back to the supply of hot water. Oneor more usage outlets are connected to the closed loop each by arelatively short length of pipe. A one-way check valve prevents drawingwater from the return line of the closed loop. Heat insulation of theclosed loop is provided to prevent unnecessary heat losses, and athermally operated switch may be used to control the operation of theclosed loop circulation pump to maintain the water in the closed loop ata predetermined temperature.

Basic Tank-Type HWR

U.S. Pat. No. 7,000,626, issued Feb. 21, 2006 to Cress, shows aninstantaneous and constant fluid delivery system and a method and meansfor maintaining a constant supply of a fluid with specificcharacteristics within a fluid supply conduit from a supply source ofthe fluid with specific characteristics at a point of service of thefluid with specific characteristics in which a first open end of arecirculation conduit is located within the fluid with specificcharacteristics supply conduit adjacent the point of service. A secondend of the recirculation conduit is connected to pump means in suchmanner that a portion of the fluid with specific characteristics withinthe fluid with specific characteristics supply conduit adjacent thepoint of service is constantly circulated back. In an alternateembodiment a similar recirculation conduit is utilized in a manner toprevent freezing of conduits in a total fluid supply line which includesportions in relatively warm areas and in areas subject to freezing.

Domestic Pipe-In-Pipe Tempering System

U.S. Pat. No. 4,917,142, issued Apr. 17, 1990 to Laing, claims asecondary circulation device for effecting secondary circulation ofwater into a hot water tank not having a return opening. The arms of aT-fitting are place in series with the distribution line near the outletport of the water tank. A return line, continuous at one end with thedistal portion of the distribution line, is continuous at the other endwith a relatively small internal line which lies within the leg of theT-fitting, one arm of the T-fitting, and extending through the outletport into the water tank. A relatively low power pump and a sinking-ballvalve are placed in series with the return line to cause the flow ofwater in the secondary circulation system to flow in one direction only.

Tank-Type HWR with Special Diverter Fitting

U.S. Pat. No. 5,735,291, issued Apr. 7, 1998 to Kaonohi, describes a hotwater re-circulating system for a building comprising a water pumpconnected between an auxiliary water return line extending from a hotwater faucet to a remote hot water heater. The water pump is controlledby a timer/switch located at the hot water faucet, so that when the hotwater faucet is opened, hot water will come out therefrom. In a secondembodiment, two water pumps are each connected between two auxiliarywater return lines extending from two hot water faucets to a remote hotwater heater. Each water pump is controlled by a timer/switch located atthe hot water faucets, so that when the hot water faucets are opened,hot water wall come out therefrom.

Direct Recirculation—Basic HWR with Remote Activation Required.

U.S. Pat. No. 6,997,200, issued Feb. 14, 2006 to King, discloses a waterconservation system which recirculates and/or recycles fluids normallylost down the drain during the time it takes for a desired temperatureto be attained for usage of the hot fluids. A recirculating/recyclingvalve, through which hot fluids may flow, has an additional port fittedto the valve body, which by positioning the handle in a singularlyunique position, fluids not at the desired temperature are sent back tothe source from which they came, to a recycling toilet tank system or toa recycling standpipe at atmospheric pressure.

This is a Hot and Cold Water Conservation System. Does not Apply toTankless HWR

U.S. Pat. No. 5,829,475, issued Nov. 3, 1998 to Acker, indicates anon-demand zone valve recirculation system. The zone valve hot waterrecirculation system generally includes a hot water source, such as anelectric or gas water heater, a conduit for enabling circulation of hotwater from hot water source to one or more plumbing fixtures andrecovery of water to the hot water source, a pump for acceleratingdelivery of hot water to the fixtures and, importantly, a zone valve forpreventing flow of water into the hot water source during standbyperiods of the hot water source. A controller, which may include anelectronic timer, is provided for causing the zone valve to open andclose and the pump to start and stop.

Tank-Type Basic HWR with Zone Valve that Opens and Closes HWR to HeatSource. Cannot be Used for Continuous Operation.

U.S. Pat. No. 7,077,155, issued Jul. 18, 2006 to Giammaria, puts forth ahot water circulating system which provides instant hot water includinga hot water source connected to one or more fixtures and a hot waterreturn line from the fixture to the hot water source including a checkvalve and a continuous circulation pump in the return line.

Standard Tank-Type HWR

U.S. Pat. No. 5,941,275, issued Aug. 24, 1999 to Laing, concerns a pumpfor periodic conveyance of the cooled-down water content of a hot waterdistribution line. The hot water distribution system incorporates a pumppositioned close to, and between each set of hot and cold water taps towhich periodically move the cooled-down water content of the hot waterdistribution line through the cold water distribution line back to thehot water tank until the total content of the hot water line has apredetermined temperature. The pump is provided with a valve responsiveto pump-generated pressure to prevent backflow when the pump is not inuse and the pressure in the cold water distribution line is lower thanthe pressure in the hot water distribution line, such as when water isdrawn through a cold water tap.

Demand Type System—Single Fixture—Hot/Cold Cross Connection

U.S. Pat. No. 4,142,515, issued Mar. 6, 1979 to Skaats, illustrates atimed water recirculation system and apparatus for effecting a timedrecirculation of the hot water in a water distribution network such asfor an apartment complex. A recirculating pump is responsive to a dropin pressure in the hot water output line of a water heater and providesrecirculation of the water in the hot water lines from the remoteapartment locations for a timed interval. After the timed interval, andafter the system has returned to the starting pressure, therecirculating pump is again ready for operation at the time of the nextuse of the hot water in the system.

Timer Based and Pressure Sensitive HWR

U.S. Pat. No. 4,450,829, issued May 29, 1984 to Morita, is for awater-saving hot water distribution system for a dwelling or otherbuilding designed to avoid the waste of water incident to letting thewater run until hot water reaches an open hot water faucet or valve.Adjacent each hot water outlet valve there is a control unit having aninlet connected to a hot water supply line from the water heater, asupply outlet connected to the hot water faucet or valve and a returnoutlet connected by a return line to an inlet of the water heater.Between the inlet and the supply outlet of the control unit there is anormally closed valve which is thermostatically controlled so as to openonly when water in the control unit is at or above a predeterminedtemperature. When a hot water faucet or valve is opened and water in thehot water supply line has cooled to a temperature below a predeterminedvalue, the control valve remains closed and water in the hot watersupply line is returned to the water heater by a circulating pump. Whenhot water reaches the control unit, the control valve isthermostatically opened so as to supply a full flow of hot water to thefaucet or outlet valve. The water circulating pump is then turned off,thereby avoiding a waste of energy that would be incident to continuousoperation of the pump. Standard Tank-Type HWR requiring control valve ateach fixture.

Most of the prior art systems are very similar to each other. Most arestandard tank-type hot water recirculation systems. Only a couple couldbe applied to tankless, but they are demand type systems thatpredominately serve a single fixture or have special controls or valves.Some of these require remote activation or sensors. Some of thesesystems have similar components and piping arrangements.

What is needed is the system of the present invention which isengineered and designed to address the complications associated withtankless water heaters and efficient hot water return. The presentinvention utilizes the modulating burner of a tankless heater toeffectively and efficiently heat the return line, avoid stand-by lossesassociated with tank-type water heaters and protect the heat exchangerof the tankless heater. Furthermore, the present invention is designedto operate without the use of auxiliary sensors, activation andassociated wiring. The invention is designed to conserve water and fuelwhile providing instantaneous hot water to every fixture group inconjunction with tankless water heater installations. The presentinvention allows the use of traditional hot water return, pump sizingand piping for tankless water heating applications.

BRIEF SUMMARY OF THE INVENTION

The objective of the invention is to facilitate traditional hot waterreturn in tankless water heating systems and eliminate the use of waterstorage tanks in potable domestic hot water recirculation systems. Thiseliminates the need for additional storage equipment in non storageapplications, specifically designed to operate with various flow andpressure sensitive heating products such as tankless water heaters.

In brief, a tankless water heater hot water return system allows the useof traditional hot water return, pump sizing and piping methodology fortankless water heating applications. As water circulates through theunit's hot water recirculation line, the device senses that the systemloop has fallen below the set point. The device then allows water topass though the device and into the heat source heat exchanger. Once thesystem set point has been satisfied, the device will turn off untilanother demand for heating cycle. This is an energy efficient device dueto low power consumption, electronic start and stop, low heatingrequirements and conservation of water.

The present invention is engineered to specifically facilitate Hot WaterRecirculation (HWR) in conjunction with Tankless Water Heaters. Thepresent system has been designed, tested and is moving towards thirdParty Approval and Manufacturing. The present system is a simple pipingarrangement with a Pump, Solenoid Valve and Electronic TemperatureControl. An alternate embodiment does not employ the Solenoid Valve.

The present invention is designed to facilitate hot water recirculationin conjunction with tankless water heaters, specifically addressing themajor issues related to tankless hot water return recirculation. Thepresent invention inherently lends itself to energy efficiency and waterconservation.

The present invention differs from all prior art inventions in severaldistinct ways:

-   1) The present system is specifically designed to facilitate Whole    House Hot Water Recirculation with Modulating Tankless Waters    Heaters. All other systems have been designed around Tank-Type    heaters and some have been adapted for use with tankless heaters.-   2) The system pump of the present invention has been sized in    accordance with tankless heater requirements, flow rates and burner    modulation.-   3) The system of the present invention protects the tankless heater    from direct recirculation HWR, which most of the prior art systems    employ. Direct recirculation in prior art systems reduces and/or    voids tankless heater warranties.-   4) The system of the present invention was designed to replace    tank-type heaters that are being used for tankless HWR. The    tank-type units do not reduce tankless warranties, but they have    enormous energy costs associated with their operation.-   5) The system of the present invention is temperature based and does    not require any external sensors, motion detectors, remote switches    and associated wiring. The system of the present invention is    totally self contained and pre-wired.-   6) The system of the present invention does not require timing    controls, processors or pattern trending. It is temperature based    with a fully adjustable differential for maximum energy efficiency.-   7) The system of the present invention is designed to operate with    either continuous or intermittent HWR Pump.-   8) The system of the present invention is a true, traditional HWR    system that does not waste energy by heating the cold water supply.    Some of these other systems utilize the cold water line, in lieu of    a separate HWR line. This method is unnecessarily heating the cold    water supply and wasting energy.

The Tankless Return Solution Hot Water Return System of the presentinvention is design engineered to address and to correct tankless waterheating systems utilizing hot water recirculation. The inventionaddresses all of the outstanding issues that result from piping tanklesswater heaters with hot water recirculation.

The present invention allows the user the ability to pipe tankless waterheaters with traditional recirculation. It eliminates the head lossesassociated with tankless heat exchangers and allows the user to utilizea small, fractional horsepower pump, further saving energy duringoperation.

The present invention utilizes the modulating burner of the tanklessheater to only use the amount of fuel necessary to heat the return line.

The present invention forces circulation through the tankless heateronly when heat is required. The present invention by-passes the tanklessheater when not heating the return line. This prevents reduction ofwarranty as constant or direct circulation is not employed.

The present invention uses built-in temperature sensing with adjustabledifferential to maximize efficiency. The invention does not require anyexternal sensors or activation. The invention works in conjunction witha timer to reduce wasted energy in non-use periods.

The present invention eliminates the use of tank-type water heaters asthe recirculation heat source. A typical hot water return line in aresidential application requires approximately 5,000 BTU per hour tomaintain a 10° F. temperature differential. Small electric tank-typewater heaters only have an input of 5118 BTU per hour at 1.5 KW. Thismeans that as long as there is circulation, the electric water heaterelement will be on, trying to maintain temperature. The presentinvention efficiently and effectively heats the hot water return linewith the tankless heater which has much greater input (199,999 BTU perhour). The invention also eliminates the stand-by losses associated withtank-type water heaters.

The present invention is designed to operate a whole-house orwhole-building recirculation. It services all fixture groups within abuilding, not just a single fixture group. The invention providesinstantaneous hot water at every fixture. Many state building codes suchas the Florida Building Code require hot water recirculation on anypiping system exceeding 100 feet in length. The invention allows usersof tankless water heaters to efficiently employ hot water recirculationwithout the negative impacts of wasted energy, reduced warranties andsingle fixture, point of use recirculation. The invention returns heatedwater back to the tankless heater instead of dumping it into the coldwater line, where it will be utilized, rather than creating more heatloss by injecting heated water into uninsulated cold water piping.

The present invention is designed to use the least possible amount ofelectricity to operate. The invention uses only 175 watts of energy infull operation and less than 100 milliamps of power in stand-by mode.Electrical energy is more expensive to operate than natural or LP gas.

The present invention uses the quick recovery of the gas fired tanklessheater to conserve energy and to effectively heat the return line.

Heat losses through circulation and radiation can be controlled byavoiding constant circulation and through insulation of hot waterpiping. As mentioned above, many state building codes also require hotwater lines to be insulated if they exceed 100 feet in length. It isgood practice to insulate all hot water lines to avoid heat loss. Theuse of timers on recirculation systems is always recommended to maximizeenergy savings. The invention is designed to provide cost-effective andenergy efficient hot water recirculation for tankless water heaters.

Water conservation is an extremely important issue today. Millions ofgallons of fresh water are wasted each year by systems that do notemploy some type of hot water recirculation. The US DOE estimates thatan average family of four can yearly waste over 10,000 gallons of waterdown the drain just waiting for hot water to arrive at the point of use.The energy consumed by maintaining a recirculation system is easilyoffset by water and sewer charges. But this only is true if an energyefficient system such as the presented invention is employed. Atank-type water heater used for recirculation with a tankless heater hasenergy costs greater than a tank-type water heater operatingstand-alone.

The present invention resolves complications that are experienced whenutilizing hot water return recirculation in conjunction with tanklesswater heaters. These issues specifically addressed by the invention are:Reduction of tankless warranties due to Direct Recirculation, Use ofTank-Type Storage Water Heaters for Tankless Hot Water Return and SingleFixture Group Recirculation requiring activation, associated sensors,switches and wiring.

The present invention exclusively resolves each and every issuecurrently affecting tankless hot water return systems. There are variousmethods that have been adapted to assist tankless hot water return, butthese methods and systems do not resolve each and every outstandingissue.

The present invention provides a design engineered, packaged pipingsystem comprising:

-   Copper or CPVC Tubing-   Non-Ferrous Fittings-   Check Valves-   Solenoid Valve(s)-   Bronze Heating Pump(s)-   Electronic Temperature Control-   Piping By-Pass for heater protection-   Built-In Temperature Sensing

The present invention provides system sizing of the heating pump andsolenoid valve to provide an acceptable flow rate during heating cycles.

The present invention incorporates the following features:

By-Pass of all return water flow away from the tankless heater instand-by (off) mode.

Utilization of the modulating burner of the tankless heater and use ofthe tankless heater as the hot water return heat source.

Compensation for tankless heat exchanger head losses to providetraditional whole-house and whole-building hot water returnrecirculation for tankless water heaters.

Built-In Temperature Control and Sensing that does not require externalcontrols, switches, sensors, timing mechanisms or remote activation.

Pump Delay Relay for controlling the system hot water return pump.

Energy Efficient design to use a minimal amount of energy to operate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other details of my invention will be described in connectionwith the accompanying drawings, which are furnished only by way ofillustration and not in limitation of the invention, and in whichdrawings:

FIG. 1 is a diagrammatic plan view of the layout of the pipingarrangement and location of each component of the present inventionshowing how the present invention is configured with specific fittingsand component locations;

FIG. 2 is a diagrammatic piping diagram and an explanation of how theinvention operates in full heating mode. This mode is active when thesystem is calling for heat in the hot water return line. This drawingindicates how the invention is piped into the tankless heater and systemhot water supply and return;

FIG. 3 is a piping diagram and an explanation of how the inventionoperates in the stand-by mode, when there is no call for heat in the hotwater return line. This drawing indicates how the invention is pipedinto the tankless heater and system hot water supply and return;

FIG. 4 is a Sequence of Operation and corresponding wiring diagram forthe invention. This written sequence of operation explains exactly howthe invention operates electrically and mechanically from the time thatpower applied until the system temperature is satisfied. The sequence ofoperation describes how the Electronic Temperature Control switchespower to turn the system on and off.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1-4, a tankless hot water return recirculation system 20(indicated by dashed rectangle in FIGS. 1-3) is integrated into atankless hot water distribution heater 30 and pipe array.

The hot water return recirculation system 20 is alternately connected toand isolated from the tankless hot water heater 30 having a cold waterfeed pipe 16 and a hot water distribution pipeline 5. The hot waterreturn recirculation system 20 comprises a recirculation pipeline 15connecting between the hot water distribution pipeline 5 and thetankless hot water heater 30 for pumping previously heated warm waterfrom the hot water distribution pipeline 5 back through therecirculation pipeline 15 to the tankless hot water heater 30 forreheating the warm water in the hot water heater to send the reheatedwater back through the hot water distribution pipeline for use. Meansfor opening and closing a pipeline connection between the hot waterdistribution pipeline and the water recirculation pipeline, which maycomprise a normally closed solenoid valve 9 in the recirculationpipeline which opens to admit heated water from the hot waterdistribution pipeline 5 into the water recirculation pipeline 15 orcloses to bypass the heater 30. Means for opening and closing a pipelineconnection between the recirculation system and the tankless hot waterheater, which may comprise a recirculation to heater by-pass valve 11cooperating with means for opening and closing the return water feedpipeline connection to the tankless hot water heater. An inline waterrecirculation pump 10 pumps the warm water from the hot waterdistribution pipeline 5 to the tankless water heater 30.

A temperature sensor 3 with a temperature indicator 2 is positioned in abrass dry well 4 in the hot water distribution pipeline 5. A two stageelectronic temperature control 2 communicates with the temperaturesensor 3, the recirculation pump 10, and the means for opening andclosing the pipeline connections 9 and 11 to activate the recirculationpump 10 to activate a flow of warm water from the hot water distributionpipeline 5 to the tankless hot water heater 30 for heating the warmwater when the warm water in the hot water distribution pipeline reachesa low set temperature and to deactivate the recirculation pump 10 andswitch back the means for opening and closing pipeline connections 9 and11 when the water temperature reaches a set high temperature to isolatethe hot water return recirculation system 15 from the tankless hot waterheater 30 and the hot water distribution pipeline 5.

A normally partially open recirculation pump valve 12 in therecirculation pipeline 15 acts as a water prime to the recirculationpump 10 and serves as a secondary by-pass line in the event of thesolenoid valve 9 failure.

A normally open cold water supply pipe 33 feeds the tankless hot waterheater 30.

The hot water pipelines 5 and 15 preferably further comprise an outerlayer of thermal insulation to minimize radiation heat loss therefrom.

The recirculation pump 10 of the present invention is structured tofunction in accordance with the tankless water heater 30 requirements,flow rates and hot water heating modulation.

The hot water return recirculation system 20 is configured for wholehouse hot water recirculation with modulating tankless water heaters 30.The hot water return recirculation system 20 protects the tankless waterheater 30 from direct recirculation from the hot water distributionpipeline 5.

The hot water return recirculation system 20 is configured to operatewith either a continuous hot water return pump or an intermittent hotwater return pump.

The hot water return recirculation system 20 is connected to themodulating burner of the tankless water heater 30 for use of thetankless water heater as a hot water return heat source.

The hot water return recirculation system 20 is connected to a tanklesswater heater 30 with a traditional hot water return. The hot waterreturn recirculation system 20 of the present invention compensates forthe head losses of the tankless heater to allow for whole-house andwhole-building hot water return.

In use in FIG. 1, the drawing depicts the invention's layout ofcomponents and their respective locations. The hot water returnrecirculation system of the present invention is a piping arrangementconstructed of CPVC or Copper Tubing with elbow and tee fittings asshown on the FIG. 1 drawing.

The system comprises a 120 Volt Pug-In Cord 1 and an ElectronicTemperature Control 2 with two stages of control. The first stagecontrols the hot water return recirculation system of the presentinvention and the second stage controls an external hot water returnpump in the tankless water heater hot water distribution pipeline. TheElectronic Temperature control 2 has a remote temperature sensor wireand sensing bulb 3. The Sensing Bulb 3 is in located in Brass Dry Well4. The Brass Dry Well 4 is immersed in the Lower By-Pass Pipe 5 of thehot water distribution pipeline to sense system return temperature.

A lower hot water return by-pass valve 6 is located on the lower by-passpipe 5 of the hot water distribution pipeline for servicing of theinvention. A hot water return check valve 7 is located on the lowerby-pass pipe 5 to insure that flow can only be directed in onedirection, away from the hot water return recirculation system and thetankless heater.

A system check valve 8 allows for flow from a tankless heating source inone direction, to mix flow with the return water that is flowing throughthe lower by-pass pipe 5. In a stand-by (off) mode there is no otherflow through the invention.

Upon a call for heating of the return line, as sensed by the sensingbulb 3 of the electronic temperature control 2, the invention isactivated for heating of the hot water return line. The electronictemperature control 2 switches power to the Solenoid Valve 9 and to theHeating Pump 10 simultaneously. The system check valve 11 only allowsflow towards the tankless heating source and prevents any backflow ofcold water.

The Upper Heating Pump Fill Valve 12 is provided for water prime to theHeating Pump 10 and also functions as a secondary by-pass line in theevent of Solenoid Valve 9 failure.

An Aquastat Relay two stage electronic temperature control 2 ispreferably provided to allow for starting and stopping the system hotwater return pump based on return temperature.

In reference to FIG. 2, the drawing is a piping diagram and anexplanation of how the invention operates in full heating mode. Thismode is active when the system is calling for heat in the hot waterreturn line. This drawing indicates how the invention is piped into thetankless heater and system hot water supply and return.

Power is applied through 120 Volt Pug-In Cord 1. Electronic TemperatureControl 2 and Temperature Sensor 3 senses hot water return temperature.The system Hot Water Return Pump 10 is circulating water from the systemsupply to the system return piping either continuously orintermittently.

If the hot water return temperature is 10° F. below the ElectronicTemperature Control 2 setpoint, the invention is activated for heatingof the hot water supply and return piping. The electronic temperaturecontrol 2 is accurate to ±1° F. The electronic temperature control 2switches power to activate the Solenoid Valve 9 and the Heating Pump 10.The Solenoid Valve 9 opens and the Heating Pump 10 begins to circulatewater towards the inlet of the tankless heater 30.

The tankless heater 30 begins to heat the flowing water and dischargesthe heated water back into the system supply pipe 5. The heated water isrecirculated from the farthest fixture group 35 back to the hot waterreturn connection of the invention 15. The system hot water return pump31 continues to circulate the heated water around the hot water loop 5.The hot water return check valve 7 and the system check valves 8 and 11only allow flow in one direction, preventing stray flow or backflow fromthe cold water inlet piping 33.

The Lower By-Pass Valve 6 is normally in the full open position and isprovided for servicing of the invention.

The Upper Heating Pump Fill Valve 12 is normally partially open toprovide water prime to the Heating Pump 10. The upper heating pump fillvalve 12 also functions as a full by-pass in the event of Solenoid Valve9 failure.

In reference to FIG. 3, the drawing is a piping diagram and anexplanation of how the invention operates in By-Pass or Off Mode. Thismode is active when the system has satisfied the call for heat in thehot water return line. This drawing indicates how the invention is pipedinto the tankless heater and system hot water supply and return.

Power is applied through 120 Volt Pug-In Cord 1. Electronic TemperatureControl 2 and Temperature Sensor 3 senses hot water return temperature.The system Hot Water Return Pump 31 is circulating water from the systemsupply to the system return piping either continuously orintermittently.

If the hot water return temperature is within 10° F. of the ElectronicTemperature Control 2 set point, the invention is deactivated forheating of the hot water supply and return piping. The electronictemperature control 2 is accurate to ±1° F. The electronic temperaturecontrol 2 disconnects power to the Solenoid Valve 9 and the Heating Pump10. The Solenoid Valve 9 closes and the Heating Pump 10 turns off tostop circulation water towards the inlet of the tankless heater 30.

The heated water is recirculated from the farthest fixture group 35 backto the hot water return connection of the invention 15. The system hotwater return pump 31 continues to circulate the heated water around thehot water loop 5. The hot water return check valve 7 and the systemcheck valves 8 and 11 will only allow flow in one direction, preventingstray flow or backflow from the cold water inlet piping 33.

The Lower By-Pass Valve 6 is normally in the full open position and isprovided for servicing of the invention.

The Upper Heating Pump Fill Valve 12 is normally partially open toprovide water prime to the Heating Pump 10. The upper heating pump fillvalve 12 also functions as a full by-pass in the event of Solenoid Valve9 failure.

In reference to FIG. 4, the drawing is a Sequence of Operation andcorresponding wiring diagram for the invention. This written sequence ofoperation explains exactly how the invention operates electrically andmechanically from the time that power applied until the systemtemperature is satisfied. The sequence of operation describes how theElectronic Temperature Control switches power to turn the system on andoff.

The system Hot Water Return Pump 1 is On for continuous operation or Offfor Pump Delay Relay.

120 Volt Power is applied through Plug-In Cord 2.

Electronic Temperature Control Sensor 3 reads a low return watertemperature of 105° F. or less.

Electronic Temperature Control 2 energizes NO Contact on Stage 2 at 105°F. to start System Hot Water Return Pump 10.

For Pump Delay Interlock, Stage 2 of the electronic temperature control2 switches external incoming 120 Volt Hot Supply from C.

Contact to NO Contact to power external Hot Water Return Pump 10.

Electronic Temperature Control Sensor 2 reads a low return watertemperature of 100° F. or less.

Electronic Temperature Control 2 switches 120 Volt power from C Contactto NO Contact on Stage 1.

Electronic Temperature Control 2 switches power to start Heating Pump 10and Solenoid Valve 9.

Electronic Temperature Control 2 senses high return water temperature of110° F. or higher.

Electronic Temperature Control 2 disconnects power at Stage 2 at 110° F.

Heating Pump 10 and Solenoid Valve 9 are de-energized and close off flowthrough the tankless heater.

Electronic Temperature Control 2 senses a high return water temperatureof 115° F. or higher.

Electronic Temperature Control 2 de-energizes NO Contact on Stage 2 at115° F.

Hot Water Return Pump 10 is deactivated.

Hot Water Return Pump Cycle repeats when temperature falls to 105° F.

Heating Cycle of hot water return line repeats when temperature falls to100° F.

In use, the premium Tankless Water Heater Hot Water Return System 20 ofthe present invention allows the use of traditional hot water return,pump sizing and piping methodology for tankless water heatingapplications. The system senses the temperature of recirculated water inthe system loop, allowing for operation of the tankless or heat sourcewhen system loop falls below a certain set point.

The premium tankless water heater hot water return system of the presentinvention is fabricated of a pre-piped, enclosed assembly containing:

-   Solenoid Control Valve 9;-   Piping 15;-   Water pump 10;-   Operator and Hot Water Return Aquastat 2;-   Valves 9, 11, 12;-   Fittings.

The components work together accordingly: As the aquastat senses theloop temperature falling, it drives a water pump to allow water to reachand activate the heating source. Once the heat source has satisfied thedemand for hot water, the aquastat senses the set point and de-energizesthe device. The unit will not allow system loop water to continuethrough the heating source.

The device may be structured so that the addition or elimination ofcertain parts may achieve similar results.

The invention may be used in either domestic or commercial applicationof potable or non potable water, utilizing many heat sources.

An ECONOMY Tankless Water Heater Hot Water Return System allows the useof traditional hot water return, pump sizing and piping methodology fortankless water heating applications. The system senses the temperatureof recirculated water in the system loop, allowing for operation of thetankless or heat source when system loop falls below a certain setpoint.

The ECONOMY tankless water heater hot water return system of the presentinvention is fabricated of a pre-piped, enclosed assembly containing:

-   Piping 15;-   Water pump 10;-   Operator and Hot Water Return Aquastat 2;-   Valves 9, 11, 12;-   Fittings.

The components work together accordingly: As the aquastat senses theloop temperature falling, it drives a water pump to allow water to reachand activate the heating source. Once the heat source has satisfied thedemand for hot water, the aquastat senses the set point and de-energizesthe device. The unit will not allow system loop water to continuethrough the heating source.

The device may be structured so that the addition or elimination ofcertain parts may achieve similar results.

The invention may be used in either domestic or commercial applicationof potable or non potable water, utilizing many heat sources.

The invention presented specifically addresses the use of TraditionalHot Water Return Recirculation with Tankless Water Heaters. Its use isnot limited to Tankless Hot Water Return as its design lends itself tovarious heating circulating uses. These uses include, but are notlimited to: Solar, Hydro Heating, Combination Heating, Indirect StorageHeaters and various other applications that require heat exchange.

Furthermore, the present invention creates a new method to correctlypipe tankless water heaters with a hot water return system. The presentinvention may be capable of achieving similar results with the additionor elimination of certain components. Any and all modifications orvariations of this method or system should be viewed as within the scopeof the presented invention.

It is understood that the preceding description is given merely by wayof illustration and not in limitation of the invention and that variousmodifications may be made thereto without departing from the spirit ofthe invention as claimed.

1. A tankless hot water return recirculation system integrated into atankless hot water distribution heater and pipe array, the systemcomprising: a hot water return recirculation system alternatelyconnected to and isolated from a tankless hot water heater having a coldwater feed pipe and a hot water distribution pipeline, the hot waterreturn recirculation system comprising a recirculation pipelineconnecting between the hot water distribution pipeline and the tanklesshot water heater for pumping previously heated warm water from the hotwater distribution pipeline back through the recirculation pipeline tothe tankless hot water heater for reheating the warm water in the hotwater heater to send the reheated water back through the hot waterdistribution pipeline for use; means for opening and closing a pipelineconnection between the hot water distribution pipeline and the waterrecirculation pipeline; means for opening and closing a pipelineconnection between the recirculation system and the tankless hot waterheater cooperating with means for opening and closing the return waterfeed pipeline connection to the tankless hot water heater; an inlinewater recirculation pump to pump the warm water from the hot waterdistribution pipeline to the tankless water heater; a temperature sensorin the hot water distribution pipeline; and a two stage electronictemperature control communicating with the temperature sensor, therecirculation pump, and the means for opening and closing the pipelineconnections to activate the recirculation pump to activate a flow ofwarm water from the hot water distribution pipeline to the tankless hotwater heater for heating the warm water when the warm water in the hotwater distribution pipeline reaches a low set temperature and todeactivate the recirculation pump and switch back the means for openingand closing pipeline connections when the water temperature reaches aset high temperature to isolate the hot water return recirculationsystem from the tankless hot water heater and the hot water distributionpipeline.
 2. The system of claim 1 wherein the means for opening andclosing the pipeline connection between the hot water distributionpipeline and the water recirculation pipeline comprises a normallyclosed solenoid valve in the recirculation pipeline which opens to admitheated water from the hot water distribution pipeline into the waterrecirculation pipeline or closes to bypass the heater.
 3. The system ofclaim 2 further comprising a normally partially open recirculation pumpvalve in the recirculation pipeline for water prime to the recirculationpump and to serve as a secondary by-pass line in the event of thesolenoid valve failure.
 4. The system of claim 1 wherein the hot waterpipelines further comprise an outer layer of thermal insulation tominimize radiation heat loss therefrom.
 5. The system of claim 1 whereinthe recirculation pump of the present invention is structured tofunction in accordance with the tankless water heater requirements, flowrates and hot water heating modulation.
 6. The system of claim 1 whereinthe hot water return recirculation system is configured for whole househot water recirculation with modulating tankless water heaters.
 7. Thesystem of claim 1 wherein the hot water return recirculation systemprotects the tankless water heater from direct recirculation from thehot water distribution pipeline.
 8. The system of claim 1 wherein thehot water return recirculation system is configured to operate with acontinuous hot water return pump.
 9. The system of claim 1 wherein thehot water return recirculation system is configured to operate with anintermittent hot water return pump.
 10. The system of claim 1 whereinthe hot water return recirculation system is connected to the modulatingburner of the tankless water heater for use of the tankless water heateras a hot water return heat source.
 11. The system of claim 1 furthercomprising a hot water return check valve located on a lower by-passpipe of the hot water distribution pipeline to insure that flow can onlybe directed in one direction, away from the tankless heater and directedtoward the hot water return and supply loop.
 12. The system of claim 1wherein the hot water return recirculation system is connected to atankless water heater with traditional hot water return.
 13. The systemof claim 1 wherein the hot water return recirculation system compensatesfor the head losses of the tankless heater to allow for whole-house andwhole-building hot water return.